Due to the amazing power of computer systems, computer systems are developed to have various functions. Input devices such as mouse devices, keyboards or a trackballs have been widely employed in a computer system for cursor control. Among these input devices, the mouse devices are the most prevailing because they are very easy-to-use. When a mouse is held on the palm of the user's hand, the user may move the mouse to control movement of the cursor shown on the computer screen. In addition, by operating the click buttons of the mouse device, the user may select a desired item on the function menu of the browsing frame or execute a corresponding function.
In the early stage, the mouse has a left click button and a right click button. With increasing development of computers and their peripheral devices, today's mouse has an additional wheel for executing a vertical scrolling function. By rotating the wheel of the mouse forwardly or backwardly, the graphic-based window or the web page shown on the computer screen may be scrolled in the vertical direction so as to facilitate the user to browse web pages or documents.
FIG. 1 is a schematic view illustrating the internal portion of a conventional wheel mouse. As shown in FIG. 1, the conventional wheel mouse principally comprises a base 10, a wheel 11, an encoder 12, a rotating shaft 13, a supporting member 14, a circuit board 15 and a switch element 16. The circuit board 15 is disposed on the base 10. The supporting member 14 pierces through the circuit board 15 and fixed on the base 10. The wheel 11 is sheathed around the rotating shaft 13 and supported by the supporting member 14. A portion of the wheel 11 is protruded from the outer surface of wheel mouse such that the wheel 11 can be rotated by a user's finger. The encoder 12 is mounted on the circuit board 15. The encoder 12 is disposed at a first side of the wheel 11. An end of the rotating shaft 13 is inserted into the encoder 12. Upon rotation of the wheel 11, the encoder 12 generates an electronic signal to the circuit board 15. In response to the electronic signal, the graphic-based window or the web page shown on the computer screen will be scrolled in the vertical direction.
Recently, the wheel mouse is developed to have expanded functions. For example, the wheel mouse may have a wheel button function. When the wheel is pressed down to trigger a specified switch element, the wheel button function is executed. An exemplary wheel button function is an automatic vertical scrolling function for automatically scrolling the graphic-based window or the web page shown on the computer screen. Please refer to FIG. 1 again. The switch element 16 is also mounted on the circuit board 15 and at a second side of the wheel 11. In a case that the wheel 11 is pressed down, the rotating shaft 13 is moved downwardly with the wheel 11. Until the rotating shaft 13 is contacted with the switch element 16 under the rotating shaft 13, the switch element 16 is triggered in order to execute the wheel button function.
The conventional wheel, however, still has some drawbacks. For example, since an end of the rotating shaft 13 is inserted into the encoder 12, the loading on the rotating shaft 13 is increased when the wheel 11 is pressed down. As such, the touch feel of depressing the wheel 11 is usually unnatural. After an extended use period, the rotating shaft 13 is readily damaged and needs to be replaced with a new one.
Moreover, the trend of designing a mouse is toward a slim type mouse. For reducing the thickness of the slim type mouse, the space within the mouse case needs to be as small as possible while maintaining the original functions of the wheel mouse. Since the encoder 12 of the conventional wheel mouse is disposed beside the wheel 12 and occupies certain space within the mouse case, the space utilization of the wheel mouse is unsatisfied.